a man 6.2 feet tall stands 12 feet away from a streetlight and casts a 5 ft shadow.

Question

How tall is the streetlight?

Answer 1

Draw a little sketch to convince yourself that the shadow of the light is 12'+ 5'=17'

Use proportions and cross product:
6.2 ft : 5 ft shadow
? ft : 17 ft shadow

height of light
= 6.2*17/5
= 21.08'